Symmetry and structure of carbon-nitrogen complexes in gallium arsenide from infrared spectroscopy and first-principles calculations

Molecular-like carbon-nitrogen complexes in GaAs are investigated both experimentally and theoretically. Two characteristic high-frequency stretching modes at \num{1973} and \SI{2060}{cm^{-1}}, detected by Fourier transform infrared absorption (FTIR) spectroscopy, appear in carbon- and nitrogen-implanted and annealed layers. From isotopic substitution it is deduced that the chemical composition of the underlying complexes is CN$_2$ and C$_2$N, respectively. Piezospectroscopic FTIR measurements reveal that both centers have tetragonal symmetry. For density functional theory (DFT) calculations linear entities are substituted for the As anion, with the axis oriented along the \hkl direction, in accordance with the experimentally ascertained symmetry. The DFT calculations support the stability of linear N-C-N and C-C-N complexes in the GaAs host crystal in the charge states ranging from $+3$ to $-3$. The valence bonds of the complexes are analyzed using molecular-like orbitals from DFT. It turns out that internal bonds and bonds to the lattice are essentially independent of the charge state. The calculated vibrational mode frequencies are close to the experimental values and reproduce precisely the isotopic mass splitting from FTIR experiments. Finally, the formation energies show that under thermodynamic equilibrium CN$_2$ is more stable than C$_2$N

Detection of fungal pathogens in viticulture by laser-induced fluorescence: Design studies on infected potted vines

We show stages of development and first results of our laser based stand-off detection system. Here, laser-induced fluorescence spectroscopy is tailored for remote detection of typical leaf-borne symptoms provoked by fungal pathogens and classification of causal agents

An Assessment of VMS-Rerouting and Traffic Signal Planning with Emission Objectives in an Urban Network – A Case Study for the City of Graz

Kölbl R, Heilmann B, Bauer D, et al. An Assessment of VMS-Rerouting and Traffic Signal Planning with Emission Objectives in an Urban Network – A Case Study for the City of Graz. In: 2015 International Conference on Models and Technologies for Intelligent Transportation Systems (MT-ITS). Piscataway, NJ: IEEE; 2015